1. Field of the Invention
The present invention relates to an apparatus for the purification of gases, in particular the removal of oil from air circulated through turboengine bearing cases.
2. Brief Description of the Prior Art
The entrainment of lubricating oil in air passing through turboengines occurs near labyrinth seals utilized to seal relatively moving elements of the turboengine due to pressure variations across the labyrinth seal structure. The oil entrained in the air presents problems regarding the operation of the turboengine, particularly the loss of bearing lubrication oil, the danger of fire should the entrained oil contact hot engine parts, and the danger of polluting cabin air circulation circuits. Even in the strongly turbulent state around the labyrinth seal structure, a mist of fine oil droplets in suspension is formed within the bearing case. Absent any effort to recover as much of this oil as possible, the amount of oil entrained in the air would be sufficient to rapidly deplete the lubricating oil reservoir, thereby limiting the operational radius of the aircraft or causing bearing failure.
Liquid separation equipment, commonly known as de-oilers, are presently used in jet turbine engines to recover as much as the entrained oil as possible. Typically, such equipment utilizes centrifugal forces to separate the oil from the air and comprises a rotor, driven by the engine shaft or otherwise, against which the gas-liquid mixture is directed. French Pat. No. 1,590,886 describes such a centrifugal separator in which a hollow rotor is provided with radial blades to centrifuge the liquid droplets from the air. A perforated sleeve located along the fins is provided with evacuation passages for removal of the recovered liquid. The purified gas is evacuated to the outside through a duct within an internal pipe.
Although the efficiency of such a device is well known, its bulk represents a substantial drawback to its efficient useage. The bulk of the device renders it difficult to place on the engine and to supply the requisite rotational force to the rotor. Although it can be mounted within the accessory support on the engine, large size conduits must be provided to limit the fluid load losses and to limit the heat leaks of the conduits passing through the main air flow. All of these factors result in an increase of the mass and complexity of the engine. The de-oiler also may be mounted against the engine shaft, but would increase the overall length of the device and necessitate an increase in the volume of the bearing sections.
Another centrifugal separation device is shown in French Pat. No. 2,033,022 wherein the oil-air mixture from the bearing cases is guided toward a central conduit fashioned within the engine shaft by forcing it to cross radial passages in such a manner that the denser oil particles are centrifugally separated. A second separation is carried out within the central passage where the particles, having acquired an eddying motion are collected along its inside wall. This device has been found to be less efficient than the previously described centrifugal separator. Furthermore, since it is integral with the shaft, it is much less amenable to installation, modification and servicing, and decreases the mechanical strength of the shaft structure.